A decorator is easier to apply to CBVs. Backwards compatibility isn't an
issue here, except for people running on a recent clone of master.
Fixed a few minor problems in the transactions docs while I was there.
Replaced them with per-database options, for proper multi-db support.
Also toned down the recommendation to tie transactions to HTTP requests.
Thanks Jeremy for sharing his experience.
Aymeric Augustin
Florian Apolloner